"We have to find the appropriate balance between getting people tested and treated for STDs, but not prescribing antibiotics to patients who don't need them," said researcher Karen Jones, an infection preventionist at St. John Hospital & Medical Center in Detroit.

Genital cultures are often collected from patients with possible symptoms of STDs, but results are not immediately available, the investigators noted.

For the study, the researchers examined the medical records of more than 1,100 patients who underwent STD testing in the emergency room.

Forty percent were treated with antibiotics for suspected gonorrhea and/or chlamydia. Of those, more than 75 percent ended up testing negative for the STDs.

Among the 60 percent of patients who did not receive antibiotics, 7 percent tested positive for one of the STDs.

The study was to be presented Thursday at the annual meeting of the Association for Professionals in Infection Control and Epidemiology, in Charlotte, N.C.

"There is a tricky balance between not furthering antibiotic resistance by over-prescribing, but also still getting people treatment for STDs they might have," Jones said in an association news release.

Experts continue to sound alarms about the overuse of antibiotics in the United States.

"According to the Centers for Disease Control and Prevention, nearly a third of antibiotics prescribed in doctors' offices, emergency rooms and hospital-based clinics in the U.S. are not needed," said Susan Dolan, association president.

"Improving the use of antibiotics is a national and international priority to help prevent antibiotic resistance, which would threaten our ability to treat even the simplest of infections," added Dolan, a hospital epidemiologist at Children's Hospital Colorado in Aurora.

Studies presented at medical meetings are usually considered preliminary until published in a peer-reviewed medical journal.

More information

The U.S. National Institute of Allergy and Infectious Diseases has more on STDs.